In seat belt devices that are equipped in vehicles, webbing for restraining passengers is wound around a belt reel and the belt reel is accommodated within a retractor in a state of being biased in a webbing winding direction (there are cases below in which this is simply referred to as a winding direction) by a winding spring. Therefore, when the webbing is fastened, the webbing is drawn out against the biasing force of the winding spring, and when the webbing is released, the webbing is wound onto the belt reel by the biasing force of the winding spring.
In recent years, seat belt devices which are provided with a motor for drawing the webbing in have been developed. In these seat belt devices, the space between the belt reel and the motor is connected by a clutch, and by blocking the clutch, the seat belt devices are configured such that only the biasing force of the winding spring acts upon the webbing while the power of the motor is not being used. Further, in these seat belt devices, when the webbing is released, by switching the clutch to be in a connected state and driving the motor, the webbing is reliably wound onto the belt reel by the biasing force of the winding spring and the driving force of the motor.
Given that, in a state in which a clutch that is used in this kind of seat belt device is connected, the motor side and the belt reel side rotate integrally only in a case in which the rotational speed in the winding direction on the motor side is greater than or equal to the rotational speed on the belt reel side, and free rotation of the belt reel side is allowed due to mutual sliding of components in a case in which the rotational speed in the winding direction on the belt reel side is greater than the rotational speed on the motor side.
However, in seat belt devices that use this kind of clutch, if the clutch is put into a connected state during winding storage of the webbing, the rotational speed on the belt reel side is fast in the initial period of winding of the webbing, and the rotational speed is faster than the rotational speed on the motor side. In this kind of circumstance, it is likely that a loud abnormal noise will be generated due to the mutual sliding of the components of the clutch. Therefore, seat belt devices that have functions that handle this phenomenon have been suggested (for example, refer to Patent Document 1).
In the seat belt device that is disclosed in Patent Document 1, during winding storage of the webbing, after winding of the webbing by the winding spring starts, there is a pause until the rotational speed on the webbing side is sufficiently reduced (is less than or equal to a predetermined speed), and thereafter, driving of the motor and connection of the clutch are performed. As a result of this, in the clutch, the generation of an abnormal noise caused by the mutual sliding of the components is suppressed since the rotational speed on the belt reel side does not become greater than the rotational speed on the motor side.